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Linux 3.14 File-System HDD Benchmarks

02-20-2014, 12:40 AM

Phoronix: Linux 3.14 File-System HDD Benchmarks

Early Linux 3.14 kernel benchmarks indicated there might be some slowdowns in disk/file-system performance for this next major kernel release. That early testing was done from an Intel ultrabook with solid-state drive while we're now in the process of carrying out more focused testing of Linux 3.14 on both HDDs and SSDs. In this article are our first hard drive benchmarks from the Linux 3.14 Git kernel compared to the stable 3.12 and 3.13 kernels.

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I've been using Btrfs daily on my main machine and my HTPC for years now. Not only have I not lost any data, but its snapshot features have saved my data numerous times (last time being around a week ago when I tried to uninstall the NVIDIA blob installed from the run script, which still leaves behind symlinks that completely stop X from starting; restore a snapshot before installing the blob and everything's back to normal).

And speaking of Btrfs, I updated my Snapper ebuilds for Gentoo Sunrise. They're still pending review, but will probably be accepted and uploaded soon enough (in the mean while they're on the bug tracker).

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I've been using Btrfs daily on my main machine and my HTPC for years now. Not only have I not lost any data, but its snapshot features have saved my data numerous times (last time being around a week ago when I tried to uninstall the NVIDIA blob installed from the run script, which still leaves behind symlinks that completely stop X from starting; restore a snapshot before installing the blob and everything's back to normal).

And speaking of Btrfs, I updated my Snapper ebuilds for Gentoo Sunrise. They're still pending review, but will probably be accepted and uploaded soon enough (in the mean while they're on the bug tracker).

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I've been using Btrfs on my laptop's SSD since Fedora 17, my home server / HTPC's main drive and its backup drive for the last few months, so far no random problems on any of them. The ONE failure I have had was related to power-loss during a system update like a year and a half ago (200+ updates and the power got killed, accidentally, during I think the kernel update)

Is my single use-case a perfect "yes! Use it!"? No, but I personally trust it more on the backup drive than I do NTFS-over-fuse quite frankly

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Thank you both for sharing, I'm going to try it with a fresh install on one of machines For the main machine, is converting existing ext4 partitions to btrfs a safe operation? Or should I backup data and go with a fresh install?

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Yes. In fact, I have a LiveCD build on SUSE Studio just for that (it automatically pulls in the latest kernel and btrfs tools for performing complex offline tasks; last time I used it to set up a backup in a different drive using btrfs-send/btrfs-receive). The btrfs check tool itself I usually run regularly to see if it reports any problems. There sometimes are some problems when I have to force-poweroff the machine (like when the GPU hangs), but they usually amount to some warnings and some data truncation. The former are mostly solved by running btrfs scrub. There was a case when it didn't help, and I needed to run the btrfs check repair to solve those. (There was also a time when btrfs check reported a lot of false positives, and even the warnings emitted now generally don't amount to much – the developers themselves can't tell what some of them are about without having direct access to the drive in question). There was also one time some years ago when I had bad RAM, which caused corruption that btrfs check repair couldn't solve either, but that's pretty much a given (and I still was able to retrieve all the data I needed).

But yes, in general, it's a good idea to run btrfs check regularly to see if there are any issues reported, also regularly check the btrfs gotchas page ( https://btrfs.wiki.kernel.org/index.php/Gotchas – one thing that is not mentioned there yet is that 3.11.10 also solves the latter balance issue) for any information on the issues in the latest FS issues, and when in doubt, go over to #btrfs on freenode and ask there.

For the main machine, is converting existing ext4 partitions to btrfs a safe operation? Or should I backup data and go with a fresh install?

Well, I never really tried it myself. Though it should be safe (once again, when in doubt, ask in #btrfs). Mind you, even if it is safe, converting is never optimal, and you're always better off doing a clean install. Besides, it's a good motivation to clean up your data

For one, right now I'm waiting for 3.14 to be released, so I could use bcache with Btrfs with my new SSD (at the moment I'm just using metadata RAID 1 between my HDD and SSD – all set up in online mode). Using bcache will require reformatting the whole thing, and by the time 3.14 is out, I'll have accumulated enough cruft for it to be worth it if only to clean up the disk and make a backup.

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I'm a bit afraid that testing on hybrid drives may give false results, because they are so unpredictable. The difference in performance may easily be 10-fold or more depending on what the drive decides to cache. I've seen cases where one day a system boots 15 seconds, and the next day it takes 3 minutes.

Small differences in models and firmware versions may give big advantages to some file systems / access patterns while heavily penalizing others. I wouldn't be surprised if NTFS was the fastest filesystem ever on such a drive, just because the drive was optimized for it.

Additionally, I don't think there is a way to clean that cache between test runs, and when testing one filesystem after the other, it may take time for the drive to notice that the hot zone to cache moved to a different place, at least in theory.

I wonder how it is in practice. It would be an interesting project to test behavior of various hybrid drives more thoroughly.